A London-based satellite broadcaster that describes itself as "the voice of authority for Muslims in the UK" has been accused of giving a platform to Anwar al-Awlaki, the extremist cleric with alleged links to al-Qaida and to the man charged with trying to blow up a transatlantic jet on Christmas Day.

The Islam Channel, a free-to-air English-language channel that claims to be "a trustworthy source to the two million-plus population of Muslims in the UK", last year carried adverts for a box set of DVDs of Awlaki's sermons and for at least two events at which the cleric was due to be the star speaker via a video link.

The channel's website has allowed visitors to click through to a pooled archive of Islamic scholars, from which they can download sermons by Awlaki, including "Stop Police Terror", "Brutality Towards Muslims" and "It's a War against Islam".

Islamic scholars have expressed concern. "Anwar al-Awlaki is asking all Muslims to unite against the west as Muslims," said Dr Irfan al-Alawi of the Centre for Islamic Pluralism. "He supports jihad to ensnare all naive, young people who get emotionally attached and go on jihadist tirades."

US intelligence agencies claim Awlaki is a key member of al-Qaida. Last week John Brennan, the US deputy national security adviser, said there were "indications" there had been direct contact between Awlaki and Umar Abdulmutallab, the 23-year-old former University College London student charged with trying to set off a bomb on a flight bound for Detroit on Christmas Day.

Awlaki has also been linked to an attack by a US army major, Nidal Malik Hasan, last November, in which 13 people died. "Mr Awlaki is a problem," Brennan said. "He's clearly a part of al-Qaida in the Arabian Peninsula. He's not just a cleric. He is trying to instigate terrorism."

Awlaki, a US-born engineer-turned-cleric, is now based in Yemen, where some reports suggest he was killed just before Christmas in a strike on a suspected al-Qaida base. His family insist he was not harmed in the raid.

Leading British Muslim organisations, including the Islamic Society of Britain, have promoted Awlaki's lectures in the past, but now condemn his views.

Haras Rafiq of Centri, a counter-extremism consultancy, said Awlaki's online influence over young radicals was becoming a serious concern. "The internet has by far overtaken TV as the favourite pastime of youngsters in countries such as the UK and the ability for people to download Awlaki's sermons is helping to provide radicalisation on demand," Rafiq said.

The channel's chief executive officer, Mohamed Ali Harrath, has been on an Interpol wanted list since 1992, after his native Tunisia accused him of attempting to create "an Islamic state by means of armed revolutionary violence". Harrath denies the charges.

A spokeswoman for the channel said it had been unaware its website had provided links to Awlaki's sermons. She said the sermons were in an online archive shared with many websites. "Islam Channel has not at any time given a platform to Mr Awlaki," she said. The channel has now removed the link.

Maajid Nawaz, a former presenter on the Islam Channel who is now director of the counter-extremism thinktank Quilliam, said: "Islam Channel is beamed into thousands of Muslim homes every night. With such influence, however, comes responsibility."